The Anterior Cruciate Ligament (ACL) in the human knee joint, commonly called Cranial Cruciate Ligament (CrCL) in the canine stifle, is frequently torn in trauma. It also frequently fails, particularly in dogs, after a degenerative process of still unknown etiology.
In human orthopedics, the standard procedure calls for replacement by an ACL allograft, a part of the patient's own patellar tendon, or a part of the tendon removed from the hamstring muscle. The procedure results in a stable knee, but the long-term performance is often unsatisfactory—75 to 90% of cases result in arthrosis of the joint within 15 years of the procedure.
In dogs, the standard procedure is either an extra capsular suture or one of several geometry modifying surgical techniques. In the extra capsular procedure, a suture is placed outside of the joint, usually on the lateral side, to approximate the function of the ligament. The intention of the suture is to provide stability of the joint for several weeks while waiting for fibrosis to form around the joint. The fibrosis should provide for long-term stability. However, the extra capsular suture technique regularly results in failure. Arthrosis of the joint, at a year or so, is the rule rather than the exception.
In surgical techniques, the tibia is cut and a segment of it is repositioned to change the geometry in order to stabilize the stifle. Various techniques have been used including: tibial plateau leveling osteotomy (TPLO; Slocum and Slocum, “Tibial Plateau Leveling Osteotomy For Repair Of Cranial Cruciate Ligament Rupture In The Canine”, Vet. Clin. North Am. 23:777-795, 1993), cranial closing wedge osteotomy (CWO; Slocum and Devine, “Cranial Tibial Wedge Osteotomy: A Technique For Eliminating Cranial Tibial Thrust In Cranial Cruciate Ligament Repair”, J. Am. Vet. Med. Assoc. 184:564-569, 1984), and tibial tuberosity advancement (TTA; Tepic et al., “Biomechanics Of The Stifle Joint”, in Proceedings of the 1st World Orthopaedic Vet. Congress, Munich, Germany, September 2002, pp 189-190). Of the surgical approaches used in dogs, TTA seems to be associated with less morbidity and faster recovery, while providing immediate and durable stability to the joint. Nevertheless, surgical complications are not uncommon with each of these techniques.
Intra-articular prostheses are also occasionally used in dogs and, currently, only on an experimental basis in humans. Again, they require highly invasive procedures to insert them within the stifle. Even then, they generally end in failure.